This invention relates to the art of manufacturing extruded articles from extrudable material such as ceramic batches, molten glasses, plastics, molten metals, and similar materials, which have the property of being able to flow or plastically deform during extrusion while being able to become sufficiently rigid immediately thereafter so as to maintain their structural integrity. More particularly, the present invention relates to an improved extrusion die, or alternatively to an improved face plate ring or mask assembly utilized in conjunction with an existing extrusion die for providing such extrusion die with greater versatility.
An extrusion die of the general type with which the present invention is useful is disclosed in U.S. Pat. No. 3,790,654 to R. D. Bagley. Disclosed therein is an extrusion die for making honeycomb structures. However, because the manufacture of such extrusion dies is complex and costly, it is desirable to provide such dies with a face plate or mask overlying a portion of the discharge face thereof so as to permit changing the overall configuration of the extruded product without necessitating the re-machining of the basic extrusion die. Such a face plate or mask is disclosed in U.S. Pat. No. 3,836,302 to R. M. Kaukeinen.
However, regardless of whether an extrusion die is utilized without a mask or face plate as disclosed in the aforementioned Bagley patent, or with a mask or face plate as disclosed in the Kaukeinen patent, it is desirable that some provision be made for improving the skin characteristics about the periphery of the cellular or honeycomb articles which are extruded by the die. Accordingly, U.S. Pat. Nos. 3,947,214 to the present applicant and 4,008,033 to Folmar et al disclose the provision of an annular recess or gap at the outlet face of an extrusion die in the face plate or mask for conrolling the flow of additional batch material to the outer boundaries or skin of an extruded honeycomb article.
While the utilization of an annular recess or gap in a face plate or mask has been generally satisfactory, it is sometimes found that the viscosity of the batch material being extruded may vary from time to time. As the batch material becomes increasingly viscous, it is sometimes determined that the width of the gap is not adequate. Alternatively, if the viscosity of the batch material decreases, the gap width may be excessive. In either case, the extruded skin of the finished honeycomb structure may be deleteriously effected. In such instances, it is generally necessary to cease the batch extrusion of certain honeycomb or cellular products, while a new mask, having the proper recess depth or gap width is obtained. Moreover, even if the viscosity of the batch material being processed remains constant, it may be desirable to increase or decrease the skin thickness of an extruded honeycomb structure depending upon the desired structural rigidity requirements and thermal shock requirements of the finished article. It would be desirable to provide a means for adapting an extrusion die mask to accommodate varying batch viscosities and varying product requirements.